The present invention relates to a novel arylamine compound and an organic electroluminescence device and, more particularly, to an organic electroluminescence device having a high luminance, excellent heat resistance, a long life and an excellent hole transporting property and emits light at a high efficiency and a novel arylamine compound providing the advantageous properties to the organic electroluminescence device.
Organic electroluminescence (referred to as EL, hereinafter) devices are used for a planar light emitting member such as a flat panel display of wall televisions and a back light of displays and the development of EL devices has been widely conducted.
Light emission from an organic substance under an electric field was observed in 1963 by Pope as light emission from a single crystal of anthracene (J. Chem. Phys., 38 (1963) 2042). In 1965, Helfinch and Schneider succeeded in observing relatively strong electroluminescence of the injection type using a solution electrode system having a good efficiency of injection (Phys. Rev. Lett., 14 (1965) 229). Since then, studies on forming organic light emitting substances from conjugated organic host substances and conjugated organic activating agents having condensed benzene rings have been reported. As the examples of the organic host substance, naphthalene, anthracene, phenanthrene, tetracene, pyrene, benzopyrene, chrysene, picene, carbazole, fluorene, biphenyl, terphenyl, triphenylene oxide, dihalobiphenyls, trans-stilbene and 1,4-diphenylbutadiene were shown. As the examples of the activating agent, anthracene, tetracene and pentacene were shown. However, these organic light emitting substances existed as a single layer having a thickness exceeding 1 xcexcm and a high electric field was required for the light emission. Therefore, studies on a thin layer device using the vacuum vapor deposition process have been conducted (for example, Thin Solid Films, 94 (1982) 171). However, a device exhibiting a sufficiently high luminance for practical application could not be obtained although the use of the thin layer was effective for decreasing the driving voltage.
Tang et al. prepared an EL device having two very thin films (a hole transporting layer and a light emitting layer) which were laminated in accordance with the vacuum vapor deposition process and disposed between the anode and the cathode and succeeded in obtaining a high luminance under a low driving voltage (Appl. Phys. Lett., 51 (1987) 913 and U.S. Pat. No. 4,356,429). Thereafter, the development of organic compounds used for the hole transporting layer and the light emitting layer was conducted for more than a dozen years and the life and the efficiency of light emission sufficient for practical application could be achieved. As the result, the practical application of the organic EL device started in the area of displays of automobile stereos and portable telephones.
However, the luminance of light emission and the durability against degradation after the use for a long time are not sufficient for practical applications and further improvements are required. In particular, when an organic El device is applied to full color displays, it is required that the luminance be as high as 300 cd/m2 or greater and a half-life be as long as several thousand hours or longer with respect to each of R, G and B colors. It is particularly difficult that these properties are achieved with respect to blue light. For the emission of blue light, the gap of the light emitting layer must be as great as 2.8 eV or greater. The energy barrier in the hole injection between the hole transporting layer and the light emitting layer is great and the intensity of the electric field applied to the interface is great. Therefore, stable hole injection cannot be achieved by using a conventional hole transporting layer and the improvement has been desired.
When application of an organic EL device to automobiles is considered, conventional organic EL devices have a problem in storage at a high temperature such as a temperature of 100xc2x0 C. or higher. Conventional hole transporting layers have low glass transition temperatures and it was found that overcoming this problem by simply raising the glass transition temperature to a temperature exceeding 100xc2x0 C. was not unsuccessful. Thus, the sufficient property for storage at high temperatures has not been achieved. Moreover, a problem arises in that exciplexes are formed by the interaction between the hole transporting layer and the light emitting layer and the luminance of the device deteriorates.
The present invention has been made to overcome the above problems and has an object of providing an organic EL device having a high luminance, excellent heat resistance, a long life and an excellent hole transporting property and emits light at a high efficiency and a novel arylamine compound providing the advantageous properties to the organic electroluminescence device.
As the result of extensive studies by the present inventors to develop an organic EL device having the above advantageous properties, it was found that, when a novel arylamine compound having a specific structure is added to the layer of organic compounds, the luminance, the heat resistance, the life and the hole transporting property of the organic EL device are improved and a high efficiency of light emission can be achieved. The present invention has been completed based on the knowledge.
The present invention provides:
A novel arylamine compound represented by the following general formula (1): 
wherein R1 and R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkoxyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 40 carbon atoms or a substituted or unsubstituted aryloxyl group having 6 to 40 carbon atom; and
Ar1 to Ar4 each independently represent a substituted or unsubstituted aryl group having 6 to 40 carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 40 carbon atoms and may represent a same group or different groups, with provisos that at least two of Ar1 to Ar4 each represent a substituted or unsubstituted m-biphenyl group or biphenyl group substituted with aryl groups and others of Ar1 to Ar4 each represent a substituted or unsubstituted biphenyl group and that, when at least two of Ar1 to Ar4 each represent biphenyl group substituted with two aryl groups, others of Ar1 to Ar4 each represent a substituted or unsubstituted aryl group; and
A novel arylamine compound represented by the following general formula (2): 
wherein at least one of A and B represents an atom group forming a substituted or unsubstituted saturated five-membered to eight-membered ring which may comprise a spiro bond, with provisos that, when any one of A and B represents an atom group forming a saturated five-membered ring, A and B each represent a group forming a ring structure or any of A and B represents a group comprising a spiro bond and that at least one of A and B represents a group which does not comprise two or more unsaturated six-membered rings; and
Ar5 to Ar8 each independently represent a substituted or unsubstituted aryl group having 6 to 40 carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 40 carbon atoms and may represent a same group or different groups.
The present invention further provides an electroluminescence device comprising a pair of electrodes and a layer of organic compounds disposed between the pair of electrodes, wherein the layer of organic compounds comprises the novel arylamine compound described above.
The novel arylamine compound of the present invention is represented by general formula (1) or general formula (2) shown above.
In general formula (1), R1 and R2 each independently represent a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkoxyl group having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 40 carbon atoms or a substituted or unsubstituted aryloxyl group having 6 to 40 carbon atom.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group and isopropyl group. Examples of the alkoxyl group include methoxyl group and ethoxyl group. Examples of the aryl group include phenyl group, biphenyl group and naphthyl group. Examples of the arylalkyl group include benzyl group, xcex1-methylbenzyl group, xcex1-ethylbenzyl group, xcex1,xcex1-dimethylbenzyl group, 4-methylbenzyl group, 4-ethylbenzyl group, 2-tert-butylbenzyl group, 4-n-octylbenzyl group, naphthylmethyl group and diphenylmethyl group. Examples of the aryloxyl group include phenoxyl group, naphthyloxyl group, anthryloxyl group, pyrenyloxyl group, fluoranthenyloxyl group, chrysenyloxyl group and perylenyloxyl group.
Examples of the substituent to the above groups include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; alkyl groups such as methyl group, ethyl group, n-propyl group and isopropyl group; alkoxyl groups such as methoxyl group and ethoxyl group; aryloxyl groups such as phenoxyl group; arylalkyl groups such as benzyl group, phenetyl group and phenylpropyl group; nitro group; cyano group; substituted amino groups such as dimethylamino group, dibenzylamino group, diphenylamino group and morpholino group; aryl groups such as phenyl group, tolyl group, biphenyl group, naphthyl group, anthryl group and pyrenyl group; and heterocyclic groups such as pyridyl group, thienyl group, furyl group, quinolyl group and carbazolyl group.
In general formula (1), Ar1 to Ar4 each independently represent a substituted or unsubstituted aryl group having 6 to 40 carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 40 carbon atoms and may represent the same group or different groups.
Examples of the aryl group include aryl groups such as phenyl group, tolyl group, biphenyl group, naphthyl group, anthryl group and pyrenyl group. Examples of the heterocyclic group include pyridyl group, thienyl group, furyl group, quinolyl group and carbazolyl group.
In general formula (1), at least two of Ar1 to Ar4 each represent a substituted or unsubstituted m-biphenyl group or biphenyl group substituted with aryl groups and the others of Ar1 to Ar4 each represent a substituted or unsubstituted biphenyl group. However, when at least two of Ar1 to Ar4 each represent biphenyl group substituted with two aryl groups, the others of Ar1 to Ar4 each represent a substituted or unsubstituted aryl group.
Examples of the substituent to the groups represented by Ar1 to Ar4 include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; alkyl groups such as methyl group, ethyl group, n-propyl group and isopropyl group; alkoxyl groups such as methoxyl group and ethoxyl group; aryloxyl groups such as phenoxyl group; arylalkyl groups such as benzyl group, phenetyl group and phenylpropyl group; nitro group; cyano group; substituted amino groups such as dimethylamino group, dibenzylamino group, diphenylamino group and morpholino group; aryl groups such as phenyl group, tolyl group, biphenyl group, naphthyl group, anthryl group and pyrenyl group; and heterocyclic groups such as pyridyl group, thienyl group, furyl group, quinolyl group and carbazolyl group.
Examples of the aryl group in the biphenyl group substituted with aryl groups include phenyl group, biphenyl group, terphenyl group, naphthyl group, anthryl group and fluorenyl group.
It is preferable that Ar1 and Ar3 each represent a substituted or unsubstituted m-biphenyl group and Ar2 and Ar4 each represent a substituted or unsubstituted biphenyl group.
In general formula (2), at least one of A and B represents an atom group forming a substituted or unsubstituted saturated five-membered to eight-membered ring which may comprise a spiro bond. When any one of A and B represents an atom group forming a saturated five-membered ring, A and B each represent a group forming a ring structure or any of A and B represents a group comprising a spiro bond. At least one of A and B represents a group which does not comprise two or more unsaturated six-membered rings.
The spiro bond described above means a structure in which two saturated cyclic structures are bonded to each other through one atom, such as a carbon atom or silicon atom, which is a member of both cyclic structures. In the novel arylamine compound, it is preferable that the atom group represented by A or B comprises a spiro bond.
Examples of the atom forming the atom group represented by A or B include carbon atom and atoms other than carbon atom such as Si, O, S, N, B and P. These atoms may form a portion of the saturated cyclic structure. The saturated cyclic structure may have substituents such as alkyl groups, alkoxyl groups and aryl groups.
Examples of the biphenyl structure comprising the atom groups represented by at least one of A and B include the following structures: 
In general formula (2), Ar5 to Ar8 each independently represent a substituted or unsubstituted aryl group having 6 to 40 carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 40 carbon atoms and may represent the same group or different groups.
Examples of the substituted or unsubstituted aryl group include phenyl group, biphenyl group, terphenyl group, naphthyl group, anthryl group, fluorenyl group and fluoranthenyl group. Examples of the substituted or unsubstituted heterocyclic group include pyridyl group, furyl group, thienyl group and carbazolyl group.
Examples of the substituent to the above groups include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; alkyl groups such as methyl group, ethyl group, n-propyl group and isopropyl group; alkoxyl groups such as methoxyl group and ethoxyl group; aryloxyl groups such as phenoxyl group; arylalkyl groups such as benzyl group, phenetyl group and phenylpropyl group; nitro group; cyano group; substituted amino groups such as dimethylamino group, dibenzylamino group, diphenylamino group and morpholino group; aryl groups such as phenyl group, tolyl group, biphenyl group, naphthyl group, anthryl group and pyrenyl group; and heterocyclic groups such as pyridyl group, thienyl group, furyl group, quinolyl group and carbazolyl group.
In the novel arylamine compound represented by general formula (2), it is preferable that at least two of Ar5 to Ar8 each represent an aromatic hydrocarbon group having 12 or more carbon atoms. As the novel arylamine compound, it is more preferable that at least two of Ar5 to Ar8 each represent a substituted or unsubstituted biphenyl groups and at least one of Ar5 to Ar8 represents a group substituted with a diarylamino group.
The organic EL device of the present invention comprises a pair of electrodes and a layer of organic compounds disposed between the pair of electrodes and the layer of organic compounds comprises the novel arylamine compound described above.
It is preferable that the layer of organic compounds is a light emitting layer or a hole transporting layer. It is also preferable that the layer of organic compounds comprises a layer comprising the novel arylamine compound described above and a light emitting material.
The luminance, the heat resistance, the life and the efficiency of light emission of the organic EL device are improved by introducing the novel arylamine compound described above into at least one of the layers in the layer of organic compounds because the arylamine compound exhibits the excellent hole transporting property so that hole injection can be achieved with stability, has a high glass transition temperature and causes little interaction with the light emitting material so that the transition without radiation due to the interaction can be prevented.
Typical examples of the novel arylamine compound of the present invention represented by general formula (1) are shown as compounds (A-1) to (A-13) and typical examples of the novel arylamine compound of the present invention represented by general formula (2) are shown as compounds (B-1) to (B-20) in the following. However, the arylamine compound of the present invention is not limited to the compounds shown as the examples. 
The organic EL device of the present invention is a device comprising a film of organic compounds having a single layer or a plurality of layers disposed between an anode and a cathode. When the film of organic compounds has a single layer, a light emitting layer is disposed between the anode and the cathode. The light emitting layer comprises a light emitting material and may further comprise a hole injecting material or an electron injecting material to transport holes injected from the anode or electrons injected from the cathode, respectively, to the light emitting material. However, it is preferable that the light emitting material has a very high fluorescent quantum efficiency and a combination of an excellent ability of transporting holes and an excellent ability of transporting electrons and can form a uniform thin film. When the film of organic compounds in the organic EL device has a plurality of layers, the organic EL device has a laminate structure of a plurality of layers such as (an anode/a hole injecting layer/a light emitting layer/a cathode), (an anode/a light emitting layer/an electron injecting layer/a cathode) and (an anode/a hole injecting layer/a light emitting layer/an electron injecting layer/a cathode).
In the light emitting layer, conventional light emitting materials, doping materials, hole injecting materials and electron injecting materials may further be used in addition to the novel arylamine compound of the present invention. It is preferable that the novel arylamine compound is introduced into a layer selected from the light emitting layer, the electron injecting layer, the hole transporting layer and the hole injecting layer in a concentration of 0.5 to 100% by weight and more preferably in a concentration of 50 to 100% by weight.
By forming the organic EL device in a multi-layer structure, decreases in the luminance and the life due to quenching can be prevented. Where necessary, light emitting materials, doping materials, hole injecting materials and electron injecting materials may be used in combination. By using other doping materials, the luminance and the efficiency of the light emission can be improved and red light or white light can be emitted. The hole injecting layer, the light emitting layer and the electron injecting layer may be each formed in a laminate structure having two or more layers. When the hole injecting layer has a laminate structure having two or more layers, a layer into which holes are injected from the electrode is called the hole injecting layer and a layer which receives the holes from the hole injecting layer and transports the holes to the light emitting layer is called the hole transporting layer. Similarly, when the electron injecting layer has a laminate structure having two or more layers, a layer into which electrons are injected from the electrode is called the electron injecting layer and a layer which receives the electrons from the hole injecting layer and transports the electrons to the light emitting layer is called the electron transporting layer. The layer is selected and used in accordance with the properties of the material such as the energy level, heat resistance and adhesion with the film of organic compounds or the metal electrodes.
As the light emitting material or a host material which can be used for the film of organic compounds in combination with the novel arylamine compound, condensed polycyclic aromatic compounds can be used. Examples of the polycyclic aromatic compound include anthracene, naphthalene, phenanthrene, pyrene, tetracene, pentacene, coronene, chrysene, fluorescein, perylene, rubrene, phthaloperylene, naphthaloperylene, perynone, phthaloperynone, naphthaloperynone, diphenylbutadiene, tetraphenylbutadiene, coumarine, oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine, cyclopentadiene, metal complexes of quinoline, metal complexes of aminoquinoline, metal complexes of benzoquinoline, imines, diphenylethylene, vinylanthracene, diaminocarbazole, pyrane, thiopyrane, polymethine, merocyanine, oxinoid compounds chelated with imidazole, quinacridone, derivatives of stilbene and fluorescent coloring agents. However, the polycyclic aromatic compound is not limited to the above compounds described as the examples.
As the conventional hole injecting material, compounds having the ability of transporting holes, exhibiting the effect of injecting holes from the anode and the excellent effect of injecting holes to the light emitting layer or the light emitting material, preventing transfer of excited particles formed in the light emitting layer into the electron injecting layer or the electron injecting material and having the excellent ability of forming a thin film are preferable. Examples of the hole injecting material include phthalocyanine derivatives, naphthalocyanine derivatives, porphyrin derivatives, triazole, imidazole, imidazolone, imdazolethione, pyrazoline, pyrazolone, tetrahydroimidazole, oxazole, oxadiazole, hydrazone, acylhydrazone, polyarylalkanes, stilbene, butadiene, triphenylamines of the benzidine type, triphenylamines of the styrylamine type, triphenylamines of the diamine type, derivatives of the above compounds and macromolecular materials such as polyvinylcarbazole, polysilane and electrically conductive macromolecular compounds. However, the hole injecting material is not limited to the compounds described above as the examples.
Among the conventional hole injecting materials which can be used in the organic EL device of the present invention, aromatic tertiary amine derivatives and phthalocyanine derivatives are more effective.
Examples of the aromatic tertiary amine derivative include triphenylamine, tritolylamine, tolyldiphenylamine, N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-(3-methylphenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine, N,N,Nxe2x80x2,Nxe2x80x2-(4-methylphenyl)-1,1xe2x80x2-phenyl-4,4xe2x80x2-diamine, N,N,Nxe2x80x2,Nxe2x80x2-(4-methylphenyl)-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine, N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-dinaphthyl-1,1xe2x80x2-biphenyl-4,4xe2x80x2-diamine, N,Nxe2x80x2-(methylphenyl)-N,Nxe2x80x2-(4-n-butylphenyl)phenanthrene-9,10-diamine, N,N-bis(4-di-4-tolylaminophenyl)-4-phenylcyclohexane and oligomers and polymers having the skeleton structure of the aromatic tertiary amine described above. However, the aromatic tertiary amine derivative is not limited to the compounds described above as the examples.
Examples of the phthalocyanine (Pc) derivative include phthalocyanine derivatives and naphthalocyanine derivatives such as H2Pc, CuPc, CoPc, NiPc, ZnPc, PdPc, FePc, MnPc, ClAlPc, ClGaPc, ClInPc, ClSnPc, Cl2SiPc, (HO)AlPc, (HO)GaPc, VOPc, TiOPc, MoOPc and GaPc-O-GaPc. However, the phthalocyanine derivative is not limited to the compounds described above as the examples.
As the conventional electron injecting material, compounds having the ability of transporting electrons, exhibiting the effect of injecting electrons from the cathode and the excellent effect of injecting electrons into the light emitting layer or the light emitting material, preventing transfer of excited particles formed in the light emitting layer into the hole injecting layer and having the excellent ability of forming a thin film are preferable. Examples of the electron injecting material include fluorenone, anthraquinodimethane, diphenoquinone, thiopyrane dioxide, oxazole, oxadiazole, triazole, imidazole, perylenetetracarboxylic acid, fluorenylidenemethane, anthrone and derivatives of these compounds. However, the electron injecting material is not limited to the compounds described above as the examples. The charge injecting property can be improved by adding an electron accepting substance to the hole injecting material or an electron donating substance to the electron injecting material.
In the organic EL device of the present invention, metal complex compounds and five-membered ring derivatives containing nitrogen are more effective as the conventional electron injecting material.
Examples of the metal complex compound include 8-hydroxyquinolinatolithium, bis(8-hydroxyquinolinato)zinc, bis(8-hydroxyquinolinato)copper, bis(8-hydroxyquinolinato)manganese, tris(8-hydroxyquinolinato)aluminum, tris(2-methyl-8-hydroxyquinolinato)aluminum, tris(8-hydroxyquinolinato)gallium, bis(10-hydroxybenzo[h]quinolinato)beryllium, bis (10-hydroxybenzo[h] quinolinato) zinc, bis (2-methyl-8-quinolinato)chlorogallium, bis(2-methyl-8-quinolinato)(o-cresolato)gallium, bis(2-methyl-8-quinolinato) (1-naphtholato)aluminum and bis(2-methyl-8-quinolinato)(2-naphtholato)gallium. However, the metal complex compound is not limited to the compounds described above as the examples.
As the five-membered ring derivative containing nitrogen, derivatives of oxazole, thiazole, oxadiazole, thiadiazole and triazole are preferable. Examples of such compounds include 2,5-bis(1-phenyl)-1,3,4-oxazole, dimethylPOPOP, 2,5-bis(1-phenyl)-1,3,4-thiazole, 2,5-bis(1-phenyl)-1,3,4-oxadiazole, 2-(4xe2x80x2-tert-butylphenyl)-5-(4xe2x80x3-biphenyl)-1,3,4-oxadiazole, 2,5-bis(1-naphthyl)-1,3,4-oxadiazole, 1,4-bis [2-(5-phenyloxadiazolyl)]benzene, 1,4-bis [2-(5-phenyloxadiazolyl)-4-tert-butylbenzene], 2-(4xe2x80x2-tert-butylphenyl)-5-(4xe2x80x3-biphenyl)-1,3,4-thiadiazole, 2,5-bis(1-naphthyl)-1,3,4-thiadiazole, 1,4-bis [2-(5-phenylthiadiazolyl)]benzene, 2-(4xe2x80x2-tert-butylphenyl)-5-(4xe2x80x3-biphenyl)-1,3,4-triazole, 2,5-bis(1-naphthyl)-1,3,4-triazole and 1,4-bis[2-(5-phenyltriazolyl)]benzene. However, the five-membered ring derivative containing nitrogen is not limited to the compounds described above as the examples.
In the present invention, a layer of an inorganic compound may be disposed between the light emitting layer and the electrode to improve the charge injecting property. As the inorganic compound used for the layer of an inorganic compound, alkali metal compounds such as fluorides and oxides of alkali metals and alkaline earth compounds can be used. Examples of the inorganic compound include LiF, Li2O, RaO, SrO, BaF2 and SrF2.
As the electrically conductive material used for the anode of the organic EL device, materials having a work function greater than 4 eV are suitable. Examples of such materials include carbon, aluminum, vanadium, iron, cobalt, nickel, tungsten, silver, gold, platinum, palladium, alloys of these metals, metal oxides used for ITO substrates and NESA substrates such as tin oxide and indium oxide and organic electrically conductive resins such as polythiophene and polypyrrole. As the electrically conductive material used for the cathode, materials having a work function smaller than 4 eV are suitable. Examples of such materials include magnesium, calcium, tin, lead, titanium, yttrium, lithium, ruthenium, manganese, aluminum and alloys of these materials. However, the materials for the electrodes are not limited to the materials described above as the examples. Examples of the alloy include magnesium/silver alloys, magnesium/indium alloys and lithium/aluminum alloys. However, the alloy is not limited to the alloys described above as the examples. The composition of the alloy is controlled by the temperature of the sources of vapor deposition, the atmosphere and the degree of vacuum and is selected suitably. The anode and the cathode may have a laminate structure having two or more layers, where necessary.
To obtain efficient light emission from the organic EL device, it is preferable that at least one face of the device is sufficiently transparent in the region of the wavelength of the light emitted by the device. It is preferable that the substrate is also transparent. The transparent electrode is prepared by using the above electrically conductive material in accordance with a suitable process such as the vapor deposition and the sputtering in a manner such that the specific transparency can be obtained. It is preferable that the electrode at the side of the light emitting face has a transmittance of the emitted light of 10% or greater. The substrate is not particularly limited as long as the substrate has a mechanical strength, shows strength at high temperatures and is transparent. Examples of the substrate include glass substrates and transparent films of resins. Examples of the transparent films include films of resins such as polyethylene, copolymers of ethylene and vinyl acetate, copolymers of ethylene and vinyl alcohol, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketones, polysulfones, polyether sulfones, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ethers, polyvinyl fluoride, copolymers of tetrafluoroethylene and ethylene, copolymers of tetrafluoroethylene and hexafluoropropylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyesters, polycarbonates, polyurethanes, polyether imides, polyimides and polypropylene.
To improve the stability of the organic EL of the present invention to heat, moisture and the atmosphere, a protective layer may be formed on the surface of the device or the entire device may be coated with a silicone oil or a resin for protection.
For forming the layers in the organic EL device, any process can be selected from dry processes for film formation such as the vacuum vapor deposition process, the sputtering process, the plasma process and the ion plating process and wet processes for film formation such as the spin coating process, the dipping process and the flow coating process. The thickness of the film is not particularly limited. It is necessary that the thickness of the film be set within a suitable range. When the thickness of the film is greater than the suitable range, it is necessary that a great voltage be applied to obtain a specific output of the light and the efficiency decreases. When the thickness of the film is smaller than the suitable range, pin holes are formed and a sufficient luminance cannot be obtained when an electric field is applied. In general, it is preferable that the thickness of the film is in the range of 5 nm to 10 xcexcm and more preferably in the range of 10 nm to 0.2 xcexcm.
When a wet process for the film formation is used, the material for forming each layer is used for forming the thin film after the material is dissolved or dispersed in a suitable solvent such as ethanol, chloroform, tetrahydrofuran and dioxane. As the solvent, any of the above solvents can be used. In any of the layers of the organic thin films, suitable resins or additives may be used for improving the properties of the films and preventing formation of pin holes. Examples of the resin which can be used include insulating resins such as polystyrene, polycarbonates, polyarylates, polyesters, polyamides, polyurethanes, polysulfones, polymethyl methacrylate, polymethyl acrylate, cellulose and copolymers of these resins; photoconductive resins such as poly-N-vinylcarbazole and polysilane; and electrically conductive resins such as polythiophene and polypyrrole. Examples of the additive include antioxidants, ultraviolet light absorbents and plasticizers.
The organic EL device of the present invention can be used, for example, for a planar light emitting member for a flat panel display of wall televisions, a back light of copiers, printers and liquid crystal displays, a light source for instruments, a display panel and a marking light.